1. Field of the Invention
The present invention relates to document processing machines and, more particularly, to document scanning requiring document registration.
2. Prior Art
Referring to FIG. 1, there is shown a perspective view of a document processing apparatus 10. The apparatus 10 could be any suitable type of document processing apparatus, such as a copier, a facsimile machine, a scanner, a computer printer, or a multifunction device having two or more functions. Referring also to FIG. 2, in this embodiment the apparatus 10 is a copier which includes an original document feed system 11 and a copy document feed system 13. A scanner or image obtainer 12 is provided under a transparent glass platen 15. The scanned information from an original document fed through the original document feed system 13 is imaged onto paper selected from paper trays 14 or 16. Paper selected from either of the paper trays 14,16 is moved by the copy document feed system 13 through the apparatus 10 by means of various belts 18 and rollers 19 schematically depicted in FIG. 2. The original document feed system 11 also comprises suitable belts and rollers for automatically moving original documents through the document system.
Various document systems require that an automatic document handling apparatus within the system operate so as to align a particular edge of a document with a given coordinate. For example, in an x-y coordinate system this could be the coordinates 0,0, on a copier platen where the scanner or copier optics have also been aligned to begin imaging at the 0,0 coordinates on the copier platen. This process of aligning the document relative to a given coordinate is known as document registration. In a manual copying operation, an original document is registered by the user with ruler markings along the sides of the platen. In systems having automatic document handling systems document registration is automatic and is generally accomplished by the use of various belts, rollers and sensors situated along the document path. If the original document is not properly registered then undesirable dark borders and shadow images may appear on the copy. Thus, while proper document registration is critical to the operation of a document processing system it is yet one of the most difficult to achieve features of an automatic document handling system. An automatic document handling system must rapidly and accurately register each original document. In general, the document registration accuracy desired is on the order of one millimeter. In addition, improper registration due to document skewing by the paper rollers can damage original documents and affect the further automatic operation of the document handler.
Various methods exist for measuring and aligning the registration of documents within a document handling system. For example, U.S. Pat No. 4,831,420 to Walsh et al. discloses a system for setting registration using pre-printed and specially constructed test. The test documents are comprised of identifying registration marks identifying registration position and a registration cutout window. Setting the registration involves registering and copying a preprinted test sheet using the document feeder in its initial and unadjusted, registration setting. The copy produced is then compared with the original test document by placing the copy of the test document under the original test document so that the test patterns on the copy are visible through the cutout window. Thus, the test patterns on the copy may be compared with the test patterns on the original revealing the amount of registration adjustment required.
Other methods that exist for setting document registration also involve the use of expensive, specially constructed, preprinted master test documents for a variety of paper sizes and test patterns. Other disadvantages to the preprinted master test document approach are lead times for printing the various test documents required and storage by the user, whether on site or by the field service engineer.
A registration detection system for measuring document registration in an apparatus having an optical reader adapted to scan a document. The system comprising a test pattern generator and a mixer for combining an output of the test pattern generator with an output of the optical reader.
A method for determining if a scanner registration problem exists in an apparatus adapted to scan a document, the method comprising the steps of: scanning a first image; combining a first test pattern with the scanned first image; and providing informative feedback resulting from the step of combining the first test pattern with the scanned first image.
A scanner device registration measuring system for determining a scanner registration problem in a scanner device. The system comprising a test pattern generator, an input document scanning device, and an image transfer system.